A year or two ago I posted some photos of a new experimental kiln lid for my large DaVinci kiln. Instead of being mortared together like the original lid, it used a compression frame to hold it together, similar to a Minnesota Flat Top design. That lid held up very well for a fair amount of time, but the bricks eventually started to crack. Seems they do not like being compressed along their narrow side. I had though this might be a problem from the beginning, and it eventually was. So this time I rebuilt the lid with the bricks being compressed from the large side, spreading the pressure out over a much larger surface area. I also mortared the bricks together so give it even more strength. The lid is made in two sections, held together by the compression frame. Making it in one big slab would be too large and cause a lot of cracking.
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The best thing about this lid is that it's now 4-1/2" thick instead of the usual 3". The added insulation should help with the efficiency of the kiln quite a bit. The lid weighs 250+ pounds, more than the original lid springs could handle, so I attached an electric hoist to raise and lower it. The hoist hangs on a piece of 1-1/4" pipe, which allows the hoist to swivel as it works, and line up in the direction it's pulling.
So far it all seems to be working well. I did my first bisque with the lid last night, and nothing fell apart. The first cone 6 firing will be in a couple of days.